1. Field of the Invention
This invention relates to thermoplastic compositions based on polyphenylene ethers, styrene polymers and polyoctenylenes, and methods of manufacturing these.
2. Description of the Prior Art
Polyphenylene ethers, also called polyphenylene oxides, are polymers with good thermal and electrical properties. Poly(2,6-dimethyl-1,4-phenylene ether) ("PPE"), in particular, has become industrially important as a component in thermoplastic molding compositions. Because of their high viscosity when molten, pure polyphenylene ethers are difficult to process. Molded pieces produced from pure polyphenylene ethers have high Vicat softening temperature low impact strength, particularly in the neighborhood of external notches.
Many means have been proposed for improving the processibility and impact strength of molded pieces from polyphenylene ethers; see German Patent No. 1,694,255 (corresponding to U.S. Pat. No. 3,361,851), German Patent No. 1,694,257 (corresponding to U.S. Pat. No. 3,383,435), and German Patent No. 1,694,290 (corresponding to U.S. Pat. No. 3,379,792). However, it has turned out that the addition of polyolefins, polystyrenes, and/or polyamides still does not yield PPE-containing compositions possessing optimal properties.
Mixtures of polyphenylene ethers with high impact polystyrenes ("HIPS") have become very important industrially (see German Patent No. 2,211,005). The thermoplastic compositions claimed in German Patent No. 2,119,301 are comprised of polyphenylene ethers plus a rubber-modified polystyrene and/or a polystyrene and a rubber. High impact strength is claimed for compositions in which the mean particle diameter of the dispersed elastomeric phase is less than circa 2 micron.
In principle, a wide variety of mixtures can be formulated from polyphenylene ethers and HIPS containing various amounts of rubbers. However, this approach is costly, because one must have available numerous different types of polystyrene in order to be able to adjust the properties of the composition as required in various application situations.
It would be simpler and easier if one could vary the properties of products comprising thermoplastic compositions by simply varying the proportions of the components when compounding mixtures comprised of: polyphenylene ethers, a single commercially available type of polystyrene, and additives to improve impact strength.
While it is possible to work rubbers into a mixture of polyphenylene ethers and styrene polymers after producing the mixture, one must contend with the fact that the form in which rubbers are ordinarily available is the ball form, and thus they are difficult to handle. Accordingly, the after-mixing technique is fraught with formidable technical difficulties.
Abandoned European OS No. 0,016,829 discloses that in addition to rubbers prepared by polymerization of butadiene and having the general formula EQU --[CH.dbd.CH--(CH.sub.2).sub.2 ].sub.x --
there are available polyalkenylenes with the general structure EQU --[CH.dbd.CH--(CH.sub.2).sub.n ].sub.x --
which can be obtained by ring-opening polymerization of cycloolefins. Here n is thus the number of ring carbon atoms minus 2. Polypentenylenes are of particular interest, because molding compositions comprised of polyphenylene ethers and polypentenylene, or comprised of polyphenylene ethers and a styrene resin which has been modified with polypentenylene would be expected to provide improved impact strength. However, apart from the fact that polypentenylene is no longer commercially available, incorporating it into a mixture based on a polyphenylene ether involves the same difficulties as does mixing-in ordinary rubbers. German OS No. 31 38 401 discloses molding compositions comprised of a polyphenylene ether and an impact-resistant modified styrene polymer, and states that molding compositions prepared according to European OS No. 0,016,829 do not have good weatherability or good impact strength. The soft component of the styrene polymer disclosed by German OS No. 31 38 401 is a polyoctenylene with a glass transition temperature below -40.degree. C. However, with such mixtures one does not achieve compositions with improved impact strength in comparison to compositions employing customarily used rubbers as the softening components.
Neither compositions based on polyphenylene ethers and polypentenylenes, nor compositions based on polyphenylene ethers and an impact-resistant modified styrene polymer with polyoctenylene as the softening component appear to provide any recognizable advantages compared with compositions with conventiond rubber. It therefore hardly seems likely that polyphenylene ether mixtures which include polyoctenylenes would be candidates for fulfilling the current demanding requirements for high impact molding compositions.
Accordingly, there is ample room for improvement in the area of thermoplastic compositions based on polyphenylene ethers. Both thermoplastic compositions based on polyphenylene ethers possessing good desirable characteristics, such as Vicat sofening temperature and high impact strength, as well as more facile methods for preparing these and being able to modify the properties as desired, are strongly felt in this art. Thus there is a notable need for polyphenylene ether based compositions characterized with high impact resistance as well as high Vicat softening temperature. There is likewise a strongly felt need for better methods of manufacturing polyphenylene ether based thermoplastic compositions where any of a variety of desired properties can be easily adjusted and modified during the manufacturing process.